Observations reveal critical interplay of interstellar dust, hydrogen

Sep 26, 2013 by Terry Devitt

Intense molecular hydrogen formation shown in near infrared image of the reflection nebula IC 63 in the constellation Cassiopeia. The white bars represent polarization seen toward stars in the background of the nebula. The largest polarization shows the most intense emission, demonstrating that hydrogen formation influences alignment of the dust grain with a magnetic field. Credit: B-G Andersson, USRA

(Phys.org) —For astrophysicists, the interplay of hydrogen—the most common molecule in the universe—and the vast clouds of dust that fill the voids of interstellar space has been an intractable puzzle of stellar evolution.

The dust, astronomers believe, is a key phase in the life cycle of stars, which are formed in dusty nurseries throughout the cosmos. But how the dust interacts with hydrogen and is oriented by the magnetic fields in deep space has proved a six-decade-long theoretical challenge.

Now, an international team of astronomers reports key observations that confirm a theory devised by University of Wisconsin-Madison astrophysicist Alexandre Lazarian and Wisconsin graduate student Thiem Hoang. The theory describes how dust grains in interstellar space, like soldiers in lock-drill formation, spin and organize themselves in the presence of magnetic fields to precisely align in key astrophysical environments.

The effort promises to untangle a theoretical logjam about key elements of the interstellar medium and underpin novel observational tactics to probe magnetic fields in space.

The new observations, conducted by a team led by B-G Andersson of the Universities Space Research Association (USRA), and their theoretical implications are to be reported in the Oct. 1, 2013 edition of the Astrophysical Journal. The observations were conducted using a variety of techniques—optical and near infrared polarimetry, high-accuracy optical spectroscopy and photometry, and sensitive imaging in the near infrared—at observatories in Spain, Hawaii, Arizona and New Mexico.

"We need to understand grain alignment if we want to make use of polarimetry as a means of investigating interstellar magnetic fields," says Lazarian, who was encouraged to attack the problem by the renowned astrophysicist Lyman Spitzer. "Spitzer himself worked on the problem extensively."

Scientists have long known that starlight becomes polarized as it shines through clouds of neatly aligned, rapidly spinning grains of interstellar dust. And the parsing of polarized light is a key observational technique. But how the grains of dust interact with hydrogen, become aligned so that starlight shining through becomes polarized, and are set spinning has been a mystery.

"While interstellar polarization has been known since 1949, the physical mechanisms behind grain alignment have been poorly understood until recently," explains Andersson. "These observations form part of a coordinated effort to—after more than 60 years—place interstellar grain alignment on a solid theoretical and observational footing."

The observations made by Andersson and his colleagues support an analytical theory posed by Lazarian and Hoang known as Radiative Alignment Torque, which describes how irregular grains can be aligned by their interaction with magnetic fields and stellar radiation. Under the theory, grains are spun, propeller-like, by photons. Their alignment is modified by magnetic fields, which orients them with respect to the field, telling an observer its direction. Impurities and defects on the dust grains produce catalytic sites for the formation of hydrogen molecules, which are subsequently ejected, creating miniature "rocket engines," also called "Purcell thrusters" after Nobel laureate Edwin Purcell, who studied grain alignment.

The theory devised by Lazarian and Hoang predicts how the molecular hydrogen thrust changes grain alignment, and was put to the test by Andersson's team of observers.

Confirming the theory, Lazarian notes, not only helps explain how interstellar dust grains align, but promises a new ability for astronomers to use polarized visible and near infrared light to reliably probe the strength and structure of magnetic fields in interstellar space, a notoriously difficult phenomenon to measure quantitatively.

Interstellar magnetic fields are ubiquitous in spiral galaxies like our Milky Way and are believed to be essential regulators of star formation and the evolution of proto-planetary disks. They also control the regulation and propagation of cosmic rays.

The murky piece of the astrophysical puzzle, says Lazarian, was how the irregular grains of interstellar dust were set in spinning motion. The observations conducted by Andersson demonstrate that intense molecular hydrogen formation on the surface of the interstellar dust grains is an important contributor to the dust grains spinning.

Hydrogen does not exist in the element's gas phase in space since the two atoms of the molecule cannot rid themselves of the formation reaction energy without a third body. The two hydrogen atoms therefore use the surfaces of dust grains as a substrate, and the force of the reaction energy is enough to set the dust grains in motion.

The new work, which was supported by the National Science Foundation, is especially timely, Lazarian says, as two new observatories—the ground-based ALMA, the Atacama Large Millimeter Array, and the space-based Planck Telescope—are poised to build on the new results.

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User comments : 28

Solid interdisciplinary work. The understanding required to dissect an observation into it's component mechanisms is seldom restricted to a single field of study. Here we have magnetic interaction, particle physics, chemical reaction with a little photonics tossed in as a catalyst.

Or you can march in and call it some variation of a circuit component, because it would have to be to validate your beliefs.

Re: "Or you can march in and call it some variation of a circuit component, because it would have to be to validate your beliefs."

It's only in the astrophysical and cosmological disciplines -- two of the most observationally challenged and hence speculative disciplines known to man -- that associating electric currents with magnetic fields is considered some sort of heresy worthy of censorship and ridicule. It would only be ethically responsible to remind the public of such things within our science journalism.

Keep in mind that Gerrit Verschuur has already identified numerous knots within the interstellar filaments at 21-cm which are apparently aligned with critical ionization velocities. That would appear to clearly support the inference that the underlying cause for the magnetic fields is indeed an electric current. It's the astrophysical discipline's choice to simply dismiss such observations. It remains to be seen if the strategy will succeed.

It's only in the astrophysical and cosmological disciplines -- two of the most observationally challenged and hence speculative disciplines known to man -- that associating electric currents with magnetic fields is considered some sort of heresy worthy of censorship and ridicule.

Associating electric currents with magnetic fields is an absolute must.

Associating magnetic fields with electric currents is alot trickier because you have to discern between the field the currents create and the field that allowed the currents to form in the first place...then figure out the interplay between the two.

no fate, in fairness to HA, while it is true that in 'secondary evolved dynamics' situations it is indeed difficult to tease out the 'chicken or egg' or which came fist the magnetic field or the electric, in 'primary dynamics' situations involving gravity, thermodynamics and pressure-producing mechanical motion, the primary 'electric flow' is created by 'flow of matter ('charged' and/or 'neutral' overall) which generates magnetic filed, so no doubt as to which came first. Eg, Earth's dynamo system begins with spinning core 'loop flow' of matter even before any magnetic field is involved/created. You get the drift. :)

The theory describes how dust grains in interstellar space, like soldiers in lock-drill formation, spin and organize themselves in the presence of magnetic fields to precisely align in key astrophysical environments.

Careful with the magnetic alignment speculations. Remember, Voyager just recently found no shift in magnetic alignment where it was predicted to exist at the Heliopause. This just shows that astrophysicists understanding of these fields and their orientations is not as solid as they'd like to think.

Realitycheck: The flux field resulting from dynamic motion of matter in a net neutral body cannot be compared to low density charged particle motion. The necessity to confine a low density current stream of Ions/electrons is a conducting medium because particles of like charge try really hard NOT to align with each other. It is the most basic property of any current, to produce one you have MAKE the particles align and move. This is why we measure magnetic flux in space, not electric current. This is why our observations of charged particle motion in the suns radial field indicate vorticies of ever increasing diameter all the way to the heliosheath (cluster mission/voyager data). The only flux present here is generated by the bulk motion of the charged particles in the plasma, hence you get turbulent eddies or a bubble like structure unless it encounters another field, in which case the particles align or accelerate and you get flux ropes or aurorae.

Please be sure to include the circuit diagram of the turbulent eddys. The particle density near earth is considerably higher than that in your interstellar circuits so in order to be scientifically valid, you will have to explain the difference in motion, how the lower particle density of your interstellar circuits produces a directionally confining field while the higher density near earth results in eddys. Cant wait, Cantdrive.

Your understanding of plasma is remedial and wrong. You even state the flux is generated by electricity, but still fail to understand the implications.

Educate me on how it really works.

"The doer alone learneth." Friedrich Nietzsche

"I am not a teacher, but an awakener." Robert Frost

"To educate is a fallacy, one can only learn." Cantdrive85

BTW, circuits and instabilities are expected and have been observed by in situ observations of inhomogeneous plasmas. There is no reason to assume low density plasmas behave differently, especially considering the large scale filamentary and cellular structures observed throughout the Universe.

cantdrive, do you really imagine that all astrophysicists are really so dumb to not consider something you've thought is interesting? That they're too ignorant to not have heard of plasmas, or how to model them? That understanding and calculation hasn't improved so much since the 50s that we're far better able to model stellar/interstellar plasmas?

Or do you just really really believe in your bible by Alfven? That he was some sort of lone genius that is above reproof? (or proof for that matter) How far did you get in your astrophysics training that you _know_ how astrophysicists think and what they know? Or are you the prophet of that lone genius that you too are above learning?

cantdrive, do you really imagine that all astrophysicists are really so dumb

Ignorant, not dumb.

That they're too ignorant to not have heard of plasmas, or how to model them?

They've heard of them, they just prefer the comfy simplicity of their theoretical ideal ionized gases.

That understanding and calculation hasn't improved so much since the 50s that we're far better able to model stellar/interstellar plasmas?

It's far better as demonstrated by Anthony Peratt's P-I-C simulations of interacting plasmas, sadly those superior models are ignored in favor of gravity models requiring 96% more invisible stuff to be invented.

That he was some sort of lone genius that is above reproof?

Nope, not at all. He even pointed to occasions where he was wrong. He is however, largely responsible for the basis of modern plasma physics as we know it. Very few men can be credited for more in the advancement of science than Alfven, it is a very short list indeed.

You all should be ashamed of yourselves. no fate started with a good comment and one troll shows up to swing things way off topic and even no fate fell into the trap.

Such a waste of what could have been good, informative, educating well thought out discussion. Guess, I should just move on. Everyone in this article has failed science so drastically there is no longer a point to a scientific discussion.

You all should be ashamed of yourselves. no fate started with a good comment and one troll shows up to swing things way off topic and even no fate fell into the trap.

Well said, but sadly that's the nature of this site. There is no effective moderation so it is swamped by crap from a few clueless idiots. There are one or two people genuinely working on "alternative" science but the majority are just arrogant fools.

The shame is your own.Off topic? Well said? The failure is in comprehension of the subject matter.When someone knows everything, there is no room left for learning."If a man will begin with certainties, he shall end in doubts; but if he will be content to begin with doubts, he shall end in certainties." —Francis Bacon

Mr Science... I get that your point is to try and call out off topic discussion, but I'm more worried about non-physicist readers who think that cantdrive/Franklins/teech et al. actually represent some sort of academic contingency. It isn't clear to the lay person that physicists actually understand plasmas sufficiently that the "plasma universe" cranks don't really have a point when they complain about physicists not understanding plasmas.

The fact that you can create a post shows how deluded and ignorant you are of the state of space science. You either aren't paying attention or choose to remain willfully ignorant of the obvious. It's more than abundantly clear that when physicists speak of "magnetic reconnection" and frozen-in magnetic fields that there is no basis in real science and is nothing more than pseudoscience dressed up to fool the LCD's.

It's far better as demonstrated by Anthony Peratt's P-I-C simulations of interacting plasmas, sadly those superior models are ignored in favor of gravity models requiring 96% more invisible stuff to be invented.

You do know that if you go to Perrat's webpage he categorically distances himself from the EU right? He knows better than to put all his eggs one basket when dealing with astrophysics, and yes his simulations, research and models are top notch.

Regarding gravity, neither electricity or magnetism can reconcile how gravity works, Halton Arp's description would be as close as either can get but it still has no definitive mechanism that wouldn't produce other noticable effects. However WRT gravity my beliefs depart the realm of practiced/modelled science because they are based in observation only, no theoretical constructs or mathematical possibilities. Just what is required for "charge = 0" bodies to interact...neutrons.

You do know that if you go to Peratt's webpage he categorically distances himself from the EU right?

First of all, I don't see how it matters. Peratt is a leading scientist in his field and has his own POV. He has however worked with and written several papers with regular EU contributors M. A. van der Sluijs and Dr. Don Scott.http://www.plasma...rth.html

And he has this to say about Scott inre to his book 'The Electric Sky'.

"It is gratifying to see the work of my mentor, Nobel Laureate Hannes Alfvén enumerated with such clarity. I am also pleased to see that Dr. Scott has given general readers such a lucid and understandable summary of my own work." Anthony Peratt

And Arp's work on redshift and quasar ejection are top notch. Many eggs, many baskets. I agree, but I'll keep my baskets free of the metaphysics of the "standard theory" eggs.

Fascinating to see Ralph Sansbury there, is he still pushing his "infinite speed of light" nonsense? Many years ago, I showed him how to test his hypothesis using the Pioneer transponder data and that it completely disproved his hypothesis. It turned out he couldn't understand it because he didn't know how to use the second derivative of a Doppler sine wave to determine the bearing of the source.

Not sure about the" infinite speed of light" in which you're referring. Thornhill does mention the force which acts upon the orbiting particles must be near instantaneous to allow for stable orbits of electrons et al. Thornhill uses this analogy;"If I can use a simple analogy, light travels slowly like the transverse ripples on a pond surface; gravity travels swiftly and longitudinally, like the speed of sound in water."The speed of light is what it is, and not necessarily the speed limit of all possible signaling throughout the universe.

It matters because he is a leading scientist in the field you would most need to support your claims, he states no affiliation to the EU because he doesn't (support your claims). Your link mentions the word "neutron" a few times, then shuffles it in with the rest of the SA particles as a dipole with "subtrons", but we know it can't be because of it's role in a nucleus (if it were a dipole one "hemisphere" would not bond to a proton). Neutrons are affected more by gravity than by E or M, are responsible for all elements past H1 and are directly proportionate to the mass of every object (that isn't theoretical). It isn't an accident that the neutral matter in any system orients equatorially to the center mass, between the poles of the dipole field.

As I said, it is outside the mainstream, but if you take away the SA particles responsible for E and M, your left with one that favors gravity as a force. The circumstantial evidence is pretty strong.

Not sure about the" infinite speed of light" in which you're referring.

Ralph used to claim that radio signals actually propagated instantaneously but the atoms in the antenna gradually built up a vibration over a time proportional to the distance from which the signal was received, thus giving the appearance of a finite speed. He had done an experiment with a Pockels Cell, failed to get an actual signal out and mistook a spike of RFI for the signal and could never get beyond the idea that he had proven Einstein wrong. Just another crank I'm afraid, but that was a long time ago.

I was not aware the validity of a given theory was based upon who "believed" it or not, here I thought data and observation were key. BTW, there is some history behind Peratt's comment and his near earth research, the poster Hannes Alfven has commented on the subject a couple times and there seems to be something odd about the situation. In re to neutrons, Thornhill makes it clear that one must also consider the medium in which matter exists to properly account for all the various situations.

Fleet, Thornhill also mentions;"Without accepting his model in its entirety, I consider Ralph Sansbury's straightforward electrical theory of magnetism and gravity to have conceptual merit."

With your crank comment you must be suggesting Einstein is a crank and cast aside all of his work due to his acknowledging the veracity of Velikovsky's claims of EM and catastrophism in their lengthy correspondence among one another.

Any eventual ToE will likely have many bits and pieces from many different men, the likelihood of any one man knowing everything is just silly. You call Sansbury a crank because he didn't find his confirmation. I ask, billions of dollars and decades later, where's your dark matter? Crank!

Thornhill also mentions;"Without accepting his model in its entirety, I consider Ralph Sansbury's straightforward electrical theory of magnetism and gravity to have conceptual merit."

"conceptual merit" is a polite way to say "nice idea, shame it doesn't work".

With your crank comment you must be suggesting Einstein is a crank

I never talked to Einstein, I spent more than a year chatting with Ralph about his experiment and various other tests that he could apply. He's a really nice chap, we had some interesting discussions but he never got as far as learning rudimentary high school calculus or any science beyond that.

You call Sansbury a crank because he didn't find his confirmation.

No, I call him a crank because he persisted in living in denial after a test which he agreed to at the start conclusively proved his hypothesis false and wilfully refused to learn the maths or even have the result explained to him in order to protect his fantasy.

"Any eventual ToE will likely have many bits and pieces from many different men, the likelihood of any one man knowing everything is just silly."

This I agree with.

"I thought data and observation were key."

This as well.

My stance regarding our disagreement on the roles of E and M in your intergalactic/stellar network of circuits isn't that I dispute the classification of charged particle flows as a current. It's that the space between the particles is too large for them to produce a field of flux that feeds back into the particle flow to influence it. The formation of flux ropes is as good an example as any of the confining/directional field plasma creates when the particle density is sufficient, however these only form inside larger fields because the particles are accelerated by existing flux.

Call or email Peratt and ask him since you refuse to believe this from a crank like me.

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